In various apparatuses such as an automobile, a spool valve driven by an actuator such as a solenoid is widely used in order to control a fluid pressure such as a hydraulic pressure. In the spool valve, when force generated by a flow of fluid acts on a spool, it may adversely affect the control. Therefore, in order to suppress such force from acting on the spool, measures such as providing a structure for guiding a direction in which the fluid flows are taken (see PTL 1). A spool valve according to a conventional example is explained below with reference to FIG. 7. FIG. 7 is a schematic sectional view showing the vicinity of a main constituent portion of the spool valve according to the conventional example.
A spool valve 600 according to the conventional example includes a valve sleeve 610 and a spool 620 that reciprocates in the axis direction in the valve sleeve 610. The spool 620 is driven by an actuator such as a solenoid.
The valve sleeve 610 includes an input port P61, an output port P62, and a discharge port P63. On the inner circumferential surface of the valve sleeve 610, a first annular convex section 611 is provided on the opposite side to the output port P62 across the input port P61, a second annular convex section 612 provided between the input port P61 and the output port P62, and a third annular convex section 613 provided between the output port P62 and the discharge port P63.
The spool 620 includes, in order from the input port P61 side toward the discharge port P63 side, a first land section 621, a first small diameter section 622, a guide section 623, a second small diameter section 624, and a second land section 625.
The spool 620 is configured to be capable of moving to a first position for discharging fluid having desired pressure from the output port P62 and a second position for discharging the fluid from the discharge port P63. FIG. 7 shows a case in which the spool 620 is located in the first position. In this case, the outer circumferential surface of the first land section 621 is in contact with the inner circumferential surface of the first annular convex section 611 and separated from the second annular convex section 612. The outer circumferential surface of the second land section 625 is in contact with the inner circumferential surface of the third annular convex section 613. Therefore, a channel leading from the input port P61 to the output port P62 is formed. A channel leading from the output port P62 to the discharge port P63 is blocked. Consequently, the fluid flowed in from the input port P61 is discharged from the output port P62 (see an arrow R10 in the figure).
Note that, when the spool 620 further moves to the second position on the left side in the figure, the outer circumferential surface of the first land section 621 is in contact with the inner circumferential surface of the second annular convex section 612 and the outer circumferential surface of the second land section 625 is separated from the third annular convex section 613. Therefore, the channel leading from the input port P61 to the output port P62 is blocked. The channel leading from the output port P62 to the discharge port P63 is formed. Consequently, the fluid is discharged from the discharge port P63.
In the conventional example, a taper surface 623a gradually decreasing in diameter from the guide section 623 toward the first land section 621 side is provided. Consequently, the fluid flowed in from the input port P61 smoothly flows toward the output port P62. Consequently, it is possible to suppress force generated by the flow of the fluid from acting on the spool 620 and adversely affecting fluid pressure control.
However, even in the spool valve 600 according to the conventional example configured as explained above, a part of the fluid flows into a region X on the opposite side to the taper surface 623a via the guide section 623. Therefore, force pushing the spool 620 toward the input port P61 side acts with a fluid pressure in the region X and adversely affects the fluid pressure control. Therefore, there is still room of improvement.